A graphene, which has a sheet structure of a monoatomic layer in which carbon atoms are arranged in a honeycomb lattice shape, exhibits quite high mobility at a room temperature, and thus is expected to be adapted for a next-generation electronics material, particularly for a channel material of a field-effect transistor (FET) of low power consumption and fast operation. However, in the graphene, since π electron conjugate expands two-dimensionally, a band gap is equal to zero and the graphene exhibits a metallic physicality, so that a practically sufficient electric current on-off ratio cannot be obtained in a transistor which uses the graphene as a channel. Therefore, in order to adapt the graphene for a transistor, it is necessary to introduce a band gap to the graphene and to make the graphene into a semiconductor.
As one of methods for introducing a band gap to a graphene, there is a method in which a two-dimensional graphene sheet is made into a strip state of several nm to several tens of nm in width and ribbonized one-dimensionally, whereby a graphene nanoribbon (GNR) is formed. It is known that, in the GNR, the band gap is opened by a quantum confined effect and that its gap size is changed depending on a ribbon width (for example, see Non-patent Document 1).
As a method for manufacturing a GNR, there are reported a method of forming by using a negative resist (hydro silsesquioxane) by electron beam lithography (for example, see Non-patent Document 2), a method of chemically cutting open a carbon nanotube (for example, see Patent Document 1), a method of forming from graphite flakes dissolved in an organic solvent by a sonochemical method (for example, see Non-patent Document 3), and so on.
In recent years, there is depicted a method in which an anthracene dimer is synthesized, vapor-deposited under ultrahigh vacuum on a metal substrate of Au or Ag that has a flat (111) crystal surface at an atomic level, and coupled/condensed by a radical reaction by substrate heating, whereby a GNR is formed in a bottom up manner (for example, see Non-patent Document 4).